Sao Kham

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10 years, 4 months ago.

How can I change string object to char array?

Hello

I am working on a program to parse a serial data. I found a program that accepts the serial data in string object type and I want to parse that data with funcing - "strtok" but it accepts only char array format. I tried to change string data to char array but my poor knowledge of C++ could not help. Please help me. Thank you! The prom is as below:

#include "mbed.h"
#include <string>

 Serial pc(USBTX, USBRX);
string b;

//char s = ",";// for deliminator
char *token; // For fetching token one after another

void callback() {
 
}

 int main() {
  //  pc.attach(&callback);
      //buffer variables
    char lezen;
 
    //if data is ready in the buffer
    while (1) {
        //read 1 character
        lezen = pc.getc();
 
        //if character is $ than it is the start of a sentence
        if (lezen == '$') {
            //so the pointer should be set to the first position
            b.clear();
 
        }
        //write buffer character to big buffer string
        b += lezen;
 
        //if the character is # than the end of the sentence is reached and some stuff has to be done
        if (lezen == '#') {
            b.erase(0,1);
            b.erase(b.length()-1,1);
            
           token = strtok(b, ","); ///*****It does not work here*************
            //Get the rest
            while( token != NULL ) 
            {
              printf( " %s\n", token );
    
               token = strtok(NULL, ",");
            }
            
            }
}
    }

I show the part that is not working with asterisk *.

I just want to parse the serial data sent like ( S1,200) into ... .like .. command = S1; parameter = 200

If there is any other better solution .. Please let me know.

Thank you for your support.

sincerely princekham

1 Answer

Andy A
10 years, 4 months ago.

The short answer is strtok(b.c_str(), ",");

std::stringc_str() returns a char* to a c style string with the same contents as the c++ string.

However it would probably be easiest to avoid c++ strings completely and use a c style char array.

#define maxInLen 64


main () {
...

  char inBuffer[maxInLen];
  int inCount = 0;
  bool startDetected = false;
  while (1) {

    inBuffer[inCount] = pc.getc();
 
        //if character is $ than it is the start of a sentence
    if (inBuffer[inCount] == '$') {
       startDetected = true;
    } else if (startDetected) {
      
                           //if the character is # than the end of the sentence is reached and some stuff has to be done
      if (inBuffer[inCount]== '#') {

         inBuffer[inCount] = 0; // change the # to a null so that the string is null terminated.

         token = strtok(inBuffer, ",");
            //Get the rest
          while( token != NULL )  {
              printf( " %s\n", token );
              token = strtok(NULL, ",");
          } 

          startDetected = false;
          inCount = 0;

      } else {  // not the end of a line

        inCount++;
        if (inCount == maxInLen) {
          pc.puts("Buffer overflow");
          inCount  = 0;
          startDetected = false;
        }
      } 

    } // end of if start char seen
  } // while loop
}

Accepted Answer